System for connecting a shaft to a joint

ABSTRACT

The invention relates to a system for connecting a shaft to a joint, and to a corresponding method, wherein a shaft journal embodied on the end of the shaft that is to be connected to the joint can be inserted into a recess of a joint connection. The aim of the invention is to be able to pre-assemble an d axially align the shaft and the recess in a simple manner. To this end, the shaft journal and the recess are adapted to each other in such a way that the shaft journal can be displaced in the recess in an essentially weak manner in a first section T 1  of the insertion path E, and a large amount of force is expended for the displacement of the shaft journal in the recess in a section T 2  of the insertion path E.

The present invention relates to a system for connecting a shaft to ajoint, in which a shaft journal configured on the end of the shaft to beconnected with the joint can be inserted into a recess of a jointconnection, as well as to a corresponding method.

The connection system according to the invention can be used, forexample, in the case of a homokinetic joint having a central recess, inwhich the joint connection is formed by the inner hub of the joint. Sucha joint is known from DE 32 27 969 C2, in which a drive shaft isaccommodated in the bore of the inner joint body and transfers thetorque by means of a longitudinal tooth system. Furthermore, a rotaryhomokinetic joint is described in DE 40 33 275 C2, which has an outerjoint part and an inner joint part, whereby the inner joint part isconnected with a rotating shaft by way of a tapered tooth system. Inorder to achieve an approximately play-free connection between the shaftand the joint, the shaft journals and the recess of the jointconnection, i.e. the intended tooth system, must be adapted to oneanother with a precise fit, so that when the shaft journal is insertedinto the recess, great friction forces must be overcome. This requiresthe use of complicated tools during assembly, in order to push the shaftinto the recess of the joint connection precisely in the axialdirection.

Since such homokinetic joints are used, for example, in motor vehicles,which are produced on an assembly line, in mass production, such acomplicated assembly is connected with significant disadvantages andcosts, particularly since there is always the risk that the shaft willnot be connected with the joint with sufficient precision in the axialdirection.

Therefore it is the task of the present invention to make it possible toconnect a shaft to a joint, in which the assembly is simplified andoperation of the joint is made possible without noteworthy radial play.

This task is accomplished, according to the invention, in the case of aconnection system of the type stated initially, essentially in that theshaft journal and the recess are adapted to one another in such a mannerthat in a first part of the insertion path, it is possible to displacethe shaft journal in the recess essentially without force, and in asecond part of the insertion path, a great expenditure of force must beapplied for displacement of the shaft journal in the recess. In thisconnection, a displacement essentially without force means that thisdisplacement can be performed by hand, essentially without anyadditional tool. This allows pre-assembly by hand, and thereforecontributes to significant simplification of connecting the shaft to thejoint. In particular, by means of this manual pre-assembly, a goodpre-alignment of shaft journal and preferably central recess is alreadyachieved. Only in a second part of the insertion path must a greaterexpenditure of force be applied, using tools, which expenditure isbrought about by means of greater friction of the shaft journal in therecess. Because of the extensive pre-assembly by hand, however, assemblyin the second part of the insertion path can be performed withrelatively simple tools. Furthermore, the shaft is already alignedcorrectly in the recess of the joint, in the axial direction, because ofthe pre-assembly, so that no tilting of the shaft in the recess occursduring further insertion.

For this purpose, it is provided, according to an advantageousembodiment of the invention, that the first part of the insertion pathamounts to at least approximately 50% of the total insertion path.Particularly preferably, the first part of the insertion path actuallyamounts to 60 to 70% of the total insertion path. The second part of theinsertion path represents the difference from the total insertion path.However, depending on the configuration of the outer surface of theshaft journal and the inner surface of the recess, in which a toothsystem is provided, for example, the optimal percentage division betweenthe first and the second part of the insertion path can also lie outsidethe stated range, according to the invention.

According to a preferred embodiment of the present invention, theessentially force-free displacement is achieved in that radial playexists between a front section of the shaft journal and an entry sectionof the central recess, in the first part of the insertion path. This hasthe result that in this first part of the insertion path, practically nofriction occurs between the shaft journal and the recess, so thatforce-free displacement of the shaft journal in the recess is possible.In the second part of the insertion path, the shaft journal and therecess are then configured to fit precisely with one another, accordingto the invention, so that great friction forces act in this region,which require a great expenditure of force for inserting the shaftjournal into the recess, and lead to a play-free connection betweenshaft and joint. For this purpose, the outer surface of the shaftjournal and/or the inner surface of the central recess can be configuredin steps, in a manner coordinated with one another.

In a further development of the connection system, a radial play betweenthe shaft journal and the recess can constantly decrease over the courseof the second part. This has the result that the expenditure of forcethat must be applied in the second part of the insertion path increaseswith the insertion depth. For this purpose, the outer surface of theshaft journal and/or the inner surface of the central recess can beconfigured conically, particularly in the second part of the insertionpath, whereby the conicity of shaft journal and recess can be different.Thus, the expenditure of force can be precisely adapted to therequirements, and particularly good centering of the shaft in thepreferably central recess of the joint can be achieved.

In order to ensure a reliable transfer of force from the shaft to thejoint in the case of a rotary homokinetic joint, for example, aprofiling for a transfer of torque can be provided on the outer surfaceof the shaft journal and the inner surface of the recess, whichprofiling is configured, for example, as a tooth system.

Preferably, the shaft journal and/or the recess can also have an endstop that indicates the end of the insertion path and reliably delimitsit. For this purpose, the shaft can have a flange at the transition tothe shaft journal, which flange rests against the face of the jointconnection after the shaft journal has been inserted into the centralrecess.

In order to prevent the shaft journal from slipping out of the recess,something that can be provoked by impacts on the joint connection orother shocks, for example, the shaft journal can be made so that it canbe locked in place in the recess, against axial displacement, accordingto the invention. This can be done by means of a cotter pin, a sleevenut that is attached to the shaft, which can be screwed onto an outsidethread of the joint connection, several screws that can be insertedthrough a flange on the shaft and fixed in place in a face of the jointconnection, or the like.

According to another embodiment of the present invention, the shaftjournal can be fixed in place in the recess by means of a split ring,which is guided in an outer groove of the joint connection, for example,and engages into a groove formed in the shaft journal through openingsprovided in the joint connection.

Furthermore, it can be provided, according to the invention, that aplacement point for a tool is provided on the ball hub and/or shaft.This can be a flange, a groove, a sleeve nut, or the like.

Furthermore, the present invention relates to a method for connecting ashaft to a joint, by means of the connection system described above,which is characterized, in particular, in that the shaft journal of theshaft is inserted by hand, for pre-assembly, in the first part of theinsertion path, and inserted into the recess, using a tool, in thesecond part of the insertion path, with which tool the requiredexpenditure of force can be applied. For this purpose, a fork wrench,for example, can be applied to a flange of the shaft and push it intothe joint connection, or to a groove of the ball hub, and push it ontothe shaft journal under robot control. Alternatively, a sleeve nut couldalso be tightened using a fork wrench.

Additional characteristics, advantages, and application possibilities ofthe present invention are evident from the following description ofexemplary embodiments, using the drawing. In this connection, all of thecharacteristics described and/or shown in the figures are an object ofthe present invention, in and of themselves, even independent of howthey are combined in the claims or their antecedents.

THE DRAWING SHOWS

FIG. 1 a shaft to be connected with a homokinetic joint shownschematically in cross-section, according to a first embodiment, and

FIG. 2 a shaft to be connected with a joint connection shownschematically in cross-section, according to a second embodiment.

The connection system 1 shown in FIG. 1 consists of a fixed homokineticjoint 2, configured as a rotary joint, and a shaft 3 for being connectedto the joint 2, which has an inner hub 4 and an outer hub 5. Tracks 6and 7, respectively, assigned to one another in pairs, in each instance,and in which balls 8 are accommodated, are provided in the inner hub 4and the outer hub 5. The balls 8 are guided in a cage 9. For thispurpose, the cage 9 has windows distributed over its circumference, inaccordance with the number of balls 8.

In the embodiment shown, the outer hub 5 is surrounded by a carrierhousing 10, with a non-positive or positive lock. To seal the joint 2, aclosure lid 11 is inserted into the carrier housing 10, which lidprevents the penetration of dirt particles into the joint 2, or the lossof lubricant, without providing additional sealing elements. On the sideopposite the balls 8, the joint 2 is sealed by means of a set of bellows12, which is fixed in place on the inner hub 4, at its radially inneredge, by means of a tie. The radially outer edge of the set of bellows12 is attached to a cap 14 that surrounds the carrier housing 10 and theouter hub 5, by means of crimping.

For a connection to a driven shaft 3 or a shaft 3 to be driven, theinner hub 4 that serves as the joint connection has a central recess 15that is provided with a profiling 16 for transferring torque. In thismanner, the inner hub 4 can be set onto a shaft journal 17 of the shaft3, for assembly of the joint 2. For this purpose, a profiling 18 thatcorresponds to the profiling 16 of the recess 15 is formed on the shaftjournal 17, which profiling engages into the profiling 16 and allowstransfer of torque. In this connection, the profilings 16, 18 can beconfigured in the form of a tooth system, for example. A particularadvantage of this arrangement consists in the fact that the joint 2 canbe completely assembled before it is connected to the shaft 3.

For this purpose, the shaft journal 17 is inserted into the centralrecess 15 until a flange 19, configured as an end stop at the transitionbetween the shaft journal 17 and the shaft 3, comes up against the outerface of the inner hub 4. In this position, the shaft 3 is fixed in placein the inner hub 4, in the axial direction, by means of a split ring orthe like, not shown. For this purpose, the split ring is set onto agroove 20 provided on the outside of the inner hub 4. The inner hub 4 ispartially perforated in the region of the groove 20, so that the splitring, not shown, engages into a correspondingly configured groove 21 inthe shaft journal 17, through this perforation, and secures the shaft 3to prevent axial slipping. Instead of this method of fixation, the shaft3 can also be fixed in place on the joint 2 in another manner, accordingto the invention. For example, a sleeve nut can be set over the flange19, the thread of which engages in a thread formed on the outside of theinner hub 4. Alternatively to this, passage bores can be provided in theflange 19, in the axial direction, which correspond to threaded openingsin the face of the inner hub 4, so that the shaft 3 can be screwed ontothe inner hub 4 of the joint 2.

In this connection, the shaft journal 17 is adapted to the centralrecess 15 in such a manner that in a first part T₁ of the insertion pathE, essentially force-free displacement of the shaft journal 17 in therecess 15 is possible, and in a second part T₂ of the insertion path E,a great expenditure of force must be applied for the displacement of theshaft journal 17 in the recess 15.

This is achieved in that a front section of the cylindrical shaftjournal 17, corresponding to the first part T₁, has a smaller outsidediameter as compared with the inside diameter of the recess 15. As aresult, there is radial play between the shaft journal 17 and the recess15 in the first part T₁ of the insertion path E, when the shaft 3 isbeing inserted, so that the shaft journal 17 can be inserted into therecess 15 without noteworthy friction forces, in this part.

At the transition to the second part T₂ of the insertion path E, a step22 is provided on the shaft journal 17, at which step the shaft journal17 makes a transition to a larger outside diameter. This outsidediameter in the second part T₂ corresponds with a precise fit to theinside diameter of the central recess 15. In this second part T₂ of theinsertion path E, the shaft journal 17 can therefore be pushed into thecentral recess 15 only with a great expenditure of force, since a greatfriction force must be overcome. For this purpose, a fork wrench, notshown, can be used, for example, which engages on the flange 19 from theside of the shaft 3, and presses the shaft 3 into the recess 15. In thecase of a sleeve nut, the insertion of the shaft journal 13 into therecess 15 in the second part T₂ of the insertion path E can take placeby means of screwing the sleeve nut onto the inner hub 4. In the lattercase, the shaft journal 17 can be pushed into the recess 15 withoutforce, until the sleeve nut engages onto the thread.

By means of this adaptation of shaft journal 17 and recess 15, theresult is achieved that essentially force-free pre-assembly by hand ismade possible, after which the shaft journal 17 is already guidedsecurely in the recess 15. In this way, tilting of shaft 3 and inner hub4 is prevented when force is applied for further insertion, by means ofwhich a play-free connection between shaft 3 and joint 2 is produced.

FIG. 2 shows another embodiment of a connection system 1′ according tothe invention, whereby only the inner hub 4′ without profiling is shownof the joint 2, for the sake of simplicity. This embodiment differs fromthe connection system 1 described above in that the inner surface of therecess 15′ is also adapted to the structure of the shaft journal 17′,and the step 22′ in the shaft journal 17′ is configured as a conicaltransition. Otherwise, the characteristics described in connection withthe connection system 1 can also be configured in the case of theconnection system 1′.

In the case of the connection system 1′, an essentially force-freedisplacement of the shaft journal 17′ in the recess 15′ is also possiblein the first part T₁ of the insertion path E. Only in the second part T₂of the insertion path, in which the shaft journal 17′ is adapted to therecess 15′ with a precise fit, is increased expenditure of forcerequired. In this embodiment, the shaft journal 17′ is mounted in therecess 15′ without play, both in the front and in the rear region. Thisresults in a particularly stable connection of the shaft 3 to the joint2. In the region of the conically narrowing step 22′, it can be providedthat the recess 15′ narrows conically to a slightly greater degree thanthe shaft journal 17′. In this way, a constantly increasing expenditureof force becomes necessary in the region of the second part T₂ of theinsertion path E, and particularly good, tilt-free centering of theshaft 3 is achieved.

However, the present invention is not limited to the embodiments ofshaft journal and recess shown in the exemplary embodiments. These canbe freely adapted to individual requirements by a person skilled in theart. Thus, for example, the shaft journal and/or the recess can beconfigured to be conical from their front end, in each instance, totheir back end, in each instance. This embodiment can be produced inparticularly simple manner. Also, instead of the end stop configured asa flange 19, a corresponding projection can be provided in the recess,for example.

Reference Symbol List:

-   1, 1′ connection system-   2 joint, fixed homokinetic joint-   3 shaft-   4, 4′ joint connection, inner hub-   5 outer hub-   6 track of the inner hub-   7 track of the outer hub-   8 balls-   9 cage-   10 carrier housing-   11 closure lid-   12 set of bellows-   13 tie-   14 cap-   15, 15′ recess-   16 profiling of the recess-   17, 17′ shaft journal-   18 profiling of the shaft journal-   19 flange, end stop-   20 groove-   21 groove-   22, 22′ step-   E insertion path-   T₁ first part of the insertion path-   T₂ second part of the insertion path

1. System for connecting a shaft (3) to a joint (2), in which a shaftjournal (17, 17′) configured on the end of the shaft (3) to be connectedwith the joint (2) can be inserted into a recess (15, 15′) of a jointconnection (4, 4′), wherein the shaft journal (17, 17′) and the recess(15, 15′) are adapted to one another in such a manner that in a firstpart (T1) of the insertion path (E), it is possible to displace theshaft journal (17, 17′) in the recess (15, 15′) essentially withoutforce, and in a second part (T2) of the insertion path (E), a greatexpenditure of force must be applied for displacement of the shaftjournal (17, 17′) in the recess (15, 15′).
 2. Connection systemaccording to claim 1, wherein the first part (T1) of the insertion path(E) amounts to at least 50%, preferably 60 to 70% of the total insertionpath (E).
 3. Connection system according to claim 1, wherein radial playexists between a front section of the shaft journal (17, 17′) and anentry section of the recess (15, 15′), in the first part (T1) of theinsertion path (E), and that in the second part (T2) of the insertionpath (E), the shaft journal (17, 17′) and the recess (15, 15′) areconfigured to fit precisely with one another.
 4. Connection systemaccording to claim 1, wherein a radial play between the shaft journal(17, 17′) and the recess (15, 15′) constantly decreases over the courseof the second part (T2) of the insertion path (E).
 5. Connection systemaccording to claim 1, wherein a profiling (16, 18) for a transfer oftorque is provided on the outer surface of the shaft journal (17, 17′)and the inner surface of the recess (15, 15′).
 6. Connection systemaccording to claim 1, wherein the shaft journal (17, 17′) and/or therecess (15, 15′) has an end stop (19).
 7. Connection system according toclaim 6, wherein the shaft (3) has a flange (19) at the transition tothe shaft journal (17, 17′), which rests against the face of the jointconnection (4, 4′) after the shaft journal (17, 17′) has been insertedinto the central recess (15, 15′).
 8. Connection system according toclaim 1, wherein the shaft journal (17, 17′) can be locked in place inthe recess (15, 15′), against axial displacement.
 9. Connection systemaccording to claim 8, wherein the shaft journal (17, 17′) can be lockedin place in the recess (15, 15′) by means of a split ring. 10.Connection system according to claim 1, wherein a placement point for atool is provided on the shaft (3) and/or on the joint connection (4,4′).
 11. Method for connecting a shaft (3) to a joint (2) by means of aconnection system (1, 1′) according to claim 1, wherein the shaftjournal (17, 17′) of the shaft (3) is inserted by hand, forpre-assembly, in the first part (T1) of the insertion path (E), andinserted into the recess (15, 15′), using a tool, in the second part(T2) of the insertion path (E).